Experimental Technology and Management

[Objective] With the rapidly increasing demand for high computing power and intelligent computing from artificial intelligence, big data, and cloud platforms, the cooling capacity of traditional air cooling technology for IT cabinets has reached its limit. The renewal and replacement of diverse computing infrastructure, such as high density, high computing power, and high thermal output, have effectively promoted the development of liquid cooling technology. Liquid cooling technology effectively improves the traditional form of air cooling and can meet the precise cooling needs of high-density cabinets and chip levels. Depth research and development of liquid cooling technology are crucial for reducing data center energy consumption and improving energy utilization efficiency. Thus far, no teaching or research experiments on single-phase immersion liquid cooling have been conducted in Chinese universities. [Methods] A comprehensive single-phase immersion liquid cooling test bench for teaching and research was constructed in this study. The detailed thermal performance was analyzed, and the associated calculation was carried out to select the circulation pump, plate heat exchanger, cooling tower, heating device, and other heat transfer equipment to establish the single-phase immersion liquid cooling system. The coolant was comparatively selected from fluorinated liquid, deionized water, and mineral oil based on the fluid thermal physical properties, fluid motion characteristics, heat exchange performance, and operational stability. Three circulation mass flow rates were designed to compare the performance difference of the proposed single-phase immersion liquid cooling unit. The circulation mass flow rate, fluid pressure, liquid height, and power consumption were monitored and utilized to control and reflect the detailed operation of the single-phase immersion liquid cooling system. After reasonable design, comparative selection, and device connection, both the primary side cooling water cycle and the secondary side coolant cycle were assembled. After the gas injection pressure and water injection tests, the airtightness and compressive strength of the established experimental system were confirmed. Meanwhile, system debugging was conducted to test the accuracy and sensitivity of the monitoring system. [Results] With the circulation mass flow rate of cooling water varying from 4.4 m~3/h to 6.4 m~3/h, the temperatures of the inlet and outlet of the coolant and cooling water have been reduced. For pressure loss, the pressure difference on the coolant side was nearly uninfluenced, whereas the maximum pressure drop was approximately 56.5 kPa on the cooling water side, with a mass flow rate of 6.4 m~3/h. The power usage efficiency of the proposed single-phase immersion cooling system was varied in the range of 1.08–1.09. The coefficient of performance of the cooling system decreased from 6.4 to 5.68, with the cooling water mass flow rate increasing from 4.4 m~3/h to 6.4 m~3/h. The efficiency of the circulation was evaluated and determined to be approximately 20% for three operation cases. [Conclusions] Generally, the performance of the single-phase liquid cooling and heat dissipation system utilized for high-computing-power data centers is thoroughly explored and analyzed, and its improvement space and application potential are evaluated. On the one hand, the present work can provide technical support for the low-carbon and efficient operation of green data centers. On the other hand, the present work can further improve the teaching practice reform of liquid cooling research-oriented experiments in data centers.